The masters of phonograph records are normally cut by the action of a transducer that converts the incoming electronic signals (derived from a microphone and amplifier system) to a lateral and/or vertical wave movement of a needle adapted to cut the record groove. A cross-feed system for establishing the groove spiral is usually based upon a screw arranged substantially radially with respect to the turntable, and carrying a nut associated with the structure supporting the transducer. The following patents have been noted as typical of the line of development of this type of system:
______________________________________ PATENT NUMBER INVENTOR DATE OF ISSUE ______________________________________ 1,218,625 Brown 1917 1,278,042 Shulman 1918 1,389,430 Gilman 1921 1,645,911 Kramer 1927 1,827,519 Hansen 1931 1,860,104 Larsen 1932 2,061,224 Democratis 1936 2,262,299 Rebold 1941 2,375,658 Johnson 1945 2,858,135 Sherwood 1958 ______________________________________
Most record players of modest cost mount the pickup transducer on a radius arm commonly referred to as a "tone arm," primarily because of the simplicity of this arrangement. Any discrepancy between the orientation and movement of the cutting transducer from that of the playback transducer produces a tendency toward a distortion of the sound emerging from the record player system. Most record-cutting machinery in commercial use provides a straight radial movement of the record-cutting transducer with respect to the axis of the turntable on which the blank is mounted. Obviously, this produces a considerable difference between the orientation and path of movement between the cutting and playback transducers. The radius arm of the playback unit produces an arcuate path, and a progressively changing angle between the tone arm and a tangent to the record groove at any time. The lateral oscillation axis of the playback transducer also varies with respect to a tangent to the record groove, for the same reason. The result of all this is that the playback needle is controlled by groove oscillations that have different reference axes from those with which the grooves were created.